1. Technical Field
This invention is concerned with a gasket coating. In particular, the invention is concerned with a gasket coating for application to a surface of a gasket to provide improved sealing by filling small cracks and fissures in the surface of the gasket and/or of the member against which the gasket seals.
2. Related Art
Gaskets are used for sealing between two members, e.g. two portions of the exhaust system of an internal combustion engine, and provide a seal around a passage which passes from one member to the other. Accordingly, a gasket has to be resilient in order to press against the members and provide a fluid-tight seal. In the case of an exhaust gasket, the seal is to prevent escape of exhaust gases and entry of air. The resilience can be provided by utilising a relatively thick layer of resilient material such as a resilient rubber-based material or graphite but, where high temperatures (above 300.degree. C.) are experienced such as in an exhaust system, many resilient materials would degrade and are not commonly used. Instead, the gasket comprises a sheet of metal, e.g. stainless steel, which is formed into resilient ridges (called “beads”) which provide the seal. Thus, when such a gasket is clamped between two members, the clamping force compresses the beads which are resiliently deformed and press against the members along the lines of the beads. However, such gaskets normally do not provide as good a seal as is desirable because the beads are unable to enter into small cracks and fissures in the members so that gases and liquids can escape past the beads. It is known, in gaskets not utilised at such high temperatures as are experienced by exhaust gaskets, to provide metal beads with a thin coating (typically less than 200 microns in thickness) of a sealing-enhancing coating which will deform under clamping pressure to fill cracks and fissures. Known sealing-enhancing coatings, however, degrade at higher temperatures so that they cannot be used on, e.g., exhaust gaskets for internal combustion engines.